A solar battery capable of converting sunlight to electric power has attracted attention as a source of energy replacing fossil fuel. Some solar batteries including a crystalline silicon substrate and some thin-film silicon solar batteries have currently been put into practical use. The former, however, is disadvantageous in high cost for manufacturing a silicon substrate, and the latter is disadvantageous in high manufacturing cost because of necessity for use of various semiconductor manufacturing gases or a complicated apparatus. Therefore, though efforts for reducing cost per generated power output have been continued by enhancing efficiency in photoelectric conversion in any solar batteries, the problems above have not yet been solved.
PTL 1 (Japanese Patent Laying-Open No. 1-220380) has proposed as a solar battery of a new type, a wet-type solar battery to which photoinduced electron transfer of a metal complex has been applied.
In this wet-type solar battery, a photoelectric conversion layer composed of an electrolytic material and a photoelectric conversion material having an absorption spectrum in a visible light region by adsorbing a photosensitizing dye is sandwiched between electrodes of two glass substrates each having the electrode on a surface thereof.
As the wet-type solar battery above is irradiated with light, electrons are generated in the photoelectric conversion layer, generated electrons are transferred to the electrode through an external electric circuit, transferred electrons are carried to the opposing electrode by ions in the electrolyte, and they return to the photoelectric conversion layer. Electric energy is taken out through such a series of flows of electrons.
PTL 2 (WO97/16838) has proposed a dye sensitized solar battery module in which a plurality of dye sensitized solar batteries are arranged as being connected in series on a glass substrate with single transparent conductive film.
An individual dye sensitized solar battery in this dye sensitized solar battery module has such a structure that a porous semiconductor layer (a porous titanium oxide layer) serving as the photoelectric conversion layer, a porous insulating layer (an intermediate porous insulating layer), and a counter electrode (a catalyst layer) are successively stacked on a transparent substrate (a glass substrate) where a transparent conductive film (an electrode) is patterned in strips. Among the dye sensitized solar batteries, adjacent dye sensitized solar batteries are connected in series to each other in such a manner that a transparent conductive film of a single dye sensitized solar battery and a counter electrode of a dye sensitized solar battery adjacent thereto are arranged to be in contact with each other.
PTL 3 (Japanese Patent Laying-Open No. 2002-367686) has proposed a dye sensitized solar battery module having such an integrated structure as having a transparent conductive film, a porous semiconductor layer, a separator, and a counter electrode conductive layer on a transparent substrate. This dye sensitized solar battery module has adopted a porous semiconductor layer constituted of a first photoelectrode composed of a dense material and a second photoelectrode composed of a porous material. By forming the first photoelectrode composed of the dense material directly under the second photoelectrode, contact of a material for the counter electrode conductive layer with the transparent conductive film is suppressed, and by providing the first photoelectrode composed of fine particles smaller in average particle size than fine particles in the material for the counter electrode conductive layer, fine particles in the counter electrode conductive layer are prevented from passing through a photoelectrode layer to reach the transparent conductive film.